It's always good to give your blog buds immediate access to the topic at hand. By embedding videos and images, you can support your point of view with visual content. For example, if you wanted someone to see the effects of chemicals in everyday life, you may want to share a link to a video like this one:
Fish are Vanishing in California
Even more instantaneous would be to embed the video or image right into your blog. An example of this might be when a chemical is difficult to acquire or far to dangerous for the classroom, you can show video of the chemical in question and its dangerous properties without needing a vent hood for your computer. Here is a video from You Tube of people throwing chunks of pure Sodium into a pond of water:
Or this one where they sacrifice a gummy bear to the gods of science:
As far as copyrights and fair use go, I have learned that as long as you are posting to an account managed by an educational network, you can post whatever you want.
I guess I could use Dropbox to allow my students access to additional resources, graphics, and literature. Additionally, students could access assignments and other related science information.